Coordinate bonding, cluster delocalization and topological criticality in a cyclic trimeric beryllium–dinitrogen complex

Le résumé fourni par la source

Fixation and coordination of molecular dinitrogen (N2) by main-group clusters offer fundamental insight into non-classical multi-centre bonding and light-metal activation pathways. Here we report a combined density-functional and ab initio study of the cyclic cluster Be3(N2)3. Geometry optimization and frequency analysis establish a stable, closed-shell Cs-symmetric trimer containing an isosceles triangular Be3 metal core coordinated end-on by three terminal N2 ligands. Energy decomposition analysis coupled with natural orbitals for chemical valence (ETS-NOCV) shows that the Be3⋯(N2)3 interaction is dominated by orbital contributions (≈60 % of attractive forces), supplemented by electrostatic attraction that together overcome Pauli repulsion. Quantum theory of atoms in molecules (QTAIM) identifies two non-nuclear attractors along the apical–basal Be–Be edges, while electron localization function (ELF) and localized orbital locator (LOL) basin analyses reveal a distinct heart-shaped trisynaptic valence basin V(Be,Be,Be) populated by ≈1.8–2.0 electrons. These topological signatures establish multi-centre σ-aromatic delocalization as the structural foundation of the central metallacycle and demonstrate that light alkaline-earth elements can support non-classical N2 coordination frameworks.

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